Method for operating an internal combustion engine

ABSTRACT

An internal combustion engine ( 1 ), especially of a motor vehicle, is described. The engine ( 1 ) is provided with a combustion chamber ( 4 ) into which fuel can be injected in a first operating mode during a compression phase and in a second operating mode during an induction phase. The engine ( 1 ) is provided with a control apparatus ( 18 ) for switching over between the operating modes. The engine ( 1 ) includes an exhaust-gas recirculation having an exhaust-gas recirculation valve ( 14 ). The engine ( 1 ) is switched by the control apparatus ( 18 ) into the first operating mode when the exhaust-gas recirculation valve ( 14 ) is jammed in the open state.

[0001] The invention relates to a method for operating an internalcombustion engine, especially of a motor vehicle, wherein fuel isinjected into a combustion chamber in a first operating mode during acompression phase and in a second operating mode during an inductionphase. In the method, there is a switchover between the operating modesand the internal combustion engine has an exhaust-gas recirculation withan exhaust-gas recirculation valve. The invention likewise relates to acorresponding internal combustion engine as well as a correspondingcontrol apparatus for an engine of this kind.

[0002] A method of this kind, an internal combustion engine of this kindand a control apparatus of this kind are all, for example, known from aso-called gasoline direct injection. There, fuel is injected into thecombustion chamber of the engine in a homogeneous operation during theinduction phase or in a stratified operation during the compressionphase. The homogeneous operation is preferably provided for thefull-load operation of the engine; whereas, the stratified operation issuitable for idle operation and part-load operation.

[0003] In an internal combustion engine of this kind, fault functionscan occur. Accordingly, it is, for example, possible that theexhaust-gas recirculation valve jams or can no longer be moved. In thiscase, it must be ensured that the engine does not go into a criticaloperating state.

OBJECT AND ADVANTAGES OF THE INVENTION

[0004] It is an object of the invention to provide a method foroperating the internal combustion engine wherein it is ensured thatfault functions of the exhaust-gas recirculation do not lead to criticaloperating states of the engine.

[0005] This object is solved in accordance with the invention in amethod of the kind mentioned initially herein in that the engine isswitched over into the first operating mode when the exhaust-gasrecirculation valve jams in the open position. The task of the inventionis solved correspondingly in an internal combustion engine and a controlapparatus of the kind mentioned initially herein.

[0006] If the exhaust-gas recirculation valve jams in the open position,then the engine is switched over into the stratified operation inaccordance with the invention. In the stratified operation, the openexhaust-gas recirculation valve can be easily considered in the control(open loop and/or closed loop) of the engine. A critical state cantherefore not occur. With the selection of the stratified operation asan emergency operation, a reliable operation of the engine is ensured.The disadvantage that in stratified operation, only a reduced torque canbe generated by the engine is greatly outweighed by the advantage of areliable operation.

[0007] In an advantageous further embodiment of the invention, theengine is switched over into the second operating mode when theexhaust-gas recirculation valve is jammed in the closed state.

[0008] If the exhaust-gas recirculation valve jams in the closed state,then the engine is switched over into the homogeneous operation inaccordance with the invention. In the homogeneous operation, and for aclosed exhaust-gas recirculation valve, the engine can be easilyoperated and especially without exceeding exhaust-gas limit values. Areliable operation of the engine is thereby provided also in this faultcase.

[0009] In a further advantageous embodiment of the invention, theexhaust-gas recirculation valve is closed in another fault function ofthe exhaust-gas recirculation and the engine is switched over into thesecond operating mode. It is especially advantageous when a jamming ofthe exhaust-gas recirculation valve is determined with the aid of asensor.

[0010] Of special significance is the realization of the method of theinvention in the form of a control element which is provided for acontrol apparatus of an engine, especially of a motor vehicle. A programis stored on the control element which is capable of being run on acomputer, especially on a microprocessor, and is suitable for executingthe method according to the invention. In this case, the invention isrealized by a program stored on the control element so that this controlelement, which is provided with the program, defines the invention inthe same way as the method which the program can carry out. Especiallyan electric storage medium can be used as a control element, forexample, a read-only-memory or a flash memory.

[0011] Further features, application possibilities and advantages of theinvention will become apparent from the following description ofembodiments of the invention which are illustrated in the drawing. Alldescribed or illustrated features define the subject matter of theinvention by themselves or in any desired combination independently oftheir summary in the patent claims or their dependency as well asindependently of their formulation or presentation in the descriptionand/or in the drawing.

EMBODIMENTS OF THE INVENTION

[0012] The single figure of the drawing shows a schematic block circuitdiagram of an embodiment of an internal combustion engine according tothe invention.

[0013] In the FIG., an internal combustion engine 1 of a motor vehicleis shown wherein a piston 2 is movable back and forth in a cylinder 3.The cylinder 3 is provided with a combustion chamber 4 which is, interalia, delimited by the piston 2, an inlet valve 5 and an outlet valve 6.An intake manifold 7 is coupled to the inlet valve 5 and an exhaust-gaspipe 8 is coupled to the outlet valve 6.

[0014] An injection valve 9 and a spark plug 10 project into thecombustion chamber 4 in the region of the inlet valve 5 and of theoutlet valve 6. Fuel can be injected into the combustion chamber 4 viathe injection valve 9. The fuel in the combustion chamber 4 can beignited with the spark plug 10.

[0015] A rotatable throttle flap 11 is mounted in the intake manifold 7and air can be supplied via the throttle flap to the intake manifold 7.The quantity of the supplied air is dependent upon the angular positionof the throttle flap 11. A catalytic converter 12 is accommodated in theexhaust-gas pipe 8 and this catalytic converter serves to purify theexhaust gases arising because of the combustion of the fuel.

[0016] An exhaust-gas recirculation pipe 13 leads from the exhaust-gaspipe 8 back to the intake manifold 7. An exhaust-gas recirculation valve14 is accommodated in the exhaust-gas recirculation pipe 13. With thisvalve 14, the quantity of the exhaust gas, which is recirculated intothe intake manifold 7, can be adjusted. The exhaust-gas recirculationpipe 13 and the exhaust-gas recirculation valve 14 define a so-calledexhaust-gas recirculation.

[0017] A tank-venting line 16 leads from a fuel tank 15 to the intakemanifold 7. A tank-venting valve 17 is mounted in the tank-venting line16 and, with this valve 17, the quantity of the fuel vapor from the fueltank 15, which is supplied to the intake manifold 7, can be adjusted.The tank-venting line 16 and the tank-venting valve 17 define aso-called tank venting.

[0018] The piston 2 is displaced by the combustion of the fuel in thecombustion chamber 4 into a back and forth movement which is transmittedto a crankshaft (not shown) and applies a torque thereto.

[0019] Input signals 19 are applied to a control apparatus 18 and thesesignals define measured operating variables of the engine 1. Forexample, the control apparatus 18 is connected to an air-mass sensor, alambda sensor, an rpm sensor and the like. Furthermore, the controlapparatus 18 is connected to an accelerator pedal sensor which generatesa signal which indicates the position of an accelerator pedal, which canbe actuated by the driver, and therefore indicates the requested torque.The control apparatus 18 generates output signals 20 with which theperformance of the engine 1 can be influenced via actuators orpositioning devices. For example, the control apparatus 18 is connectedto the injection valve 9, the spark plug 10 and the throttle flap 11 andthe like and generates the signals required to drive the same.

[0020] The control apparatus 18 is, inter alia, provided to control(open loop and/or closed loop) the operating variables of the engine 1.For example, the fuel mass, which is injected by the injection valve 9into the combustion chamber 4, is controlled (open loop and/or closedloop) by the control apparatus 18 especially with respect to a low fuelconsumption and/or a low development of toxic substances. For thispurpose, the control apparatus 18 is provided with a microprocessor inwhich a program is stored in a memory medium, especially in a flashmemory, and this program is suited to execute the above-mentionedcontrol (open loop and/or closed loop).

[0021] The engine 1 of FIG. 1 can be operated in a plurality ofoperating modes. Accordingly, it is possible to operate the engine 1 ina homogeneous mode of operation, a stratified mode of operation, ahomogeneous lean operation and the like.

[0022] In the homogeneous operation, the fuel is injected by theinjection valve 9 during the induction phase directly into thecombustion chamber 4 of the engine 1. The fuel is thereby substantiallyswirled up to ignition so that an essentially homogeneous air/fuelmixture arises in the combustion chamber 4. The torque to be generatedis adjusted by the control apparatus 18 essentially via the position ofthe throttle flap 11. In homogeneous operation, the operating variablesof the engine 1 are so controlled (open loop and/or closed loop) thatlambda is equal to one. The homogeneous operation is especially used atfull load.

[0023] The homogeneous lean operation corresponds substantially to thehomogeneous operation, however, the lambda is set to a value of lessthan one.

[0024] In stratified operation, the fuel is injected by the injectionvalve 9 directly into the combustion chamber 4 of the engine 1 duringthe compression phase. In this way, no homogeneous mixture is present inthe combustion chamber 4 with the ignition by the spark plug 10;instead, a fuel stratification is present. The throttle flap 11 can becompletely opened except for requests, for example, of the exhaust-gasrecirculation and/or of the tank venting and the engine 1 can thereby beoperated dethrottled. The torque to be generated is, in stratifiedoperation, substantially adjusted via the fuel mass. With the stratifiedoperation, the engine 1 can be operated especially at idle and at partload.

[0025] There can be a back and forth switching or switchover between theabove-mentioned operating modes of the engine 1. Such switchovers areexecuted by the control apparatus 18.

[0026] In the operation of the engine 1, faults in the exhaust-gasrecirculation can occur, which trigger different fault reactions. Here,at least three cases can be distinguished.

[0027] (1) The exhaust-gas recirculation valve 14 jams in the open stateand can therefore no longer be closed. If an exhaust-gas recirculationvalve 14, which jams in the open state, is determined, for example, by aposition sensor or other measures, then the engine 1 is switched intothe stratified operation. In the stratified operation, the engine 1 canbe operated with limited engine power even with an open exhaust-gasrecirculation valve 14 so that an emergency operation is possible. Theexhaust-gas limit values can be maintained.

[0028] (2) The exhaust-gas recirculation valve 14 jams in the closedstate and can no longer be opened. If an exhaust-gas recirculation valve14 jammed in the closed state is determined, then the engine 1 isswitched over into the homogeneous operation. In the homogeneousoperation, the engine 1 can be easily operated with the exhaust-gasrecirculation valve 14 closed without exceeding exhaust-gas limitvalues. Basically, the stratified operation would also be possible, buthere, prescribed exhaust-gas limit values, if required, could no longerbe maintained.

[0029] (3) Some other fault is determined in the exhaust-gasrecirculation or in the control (open loop and/or closed loop) of theexhaust-gas recirculation and the exhaust-gas recirculation valve 14 canbe closed. In this case, the engine 1 is switched over into thehomogeneous operation and the exhaust-gas recirculation valve 14 isclosed. As already explained, the engine 1 can be easily operated in thehomogeneous operation even with a closed exhaust-gas recirculation valve14 without affecting exhaust-gas limit values.

[0030] The determination of a fault in the exhaust-gas recirculation oron the exhaust-gas recirculation valve 14 can take place directly orindirectly by the control apparatus 18 with the aid of sensors and/orvia the diagnosis of the actuator which drives the exhaust-gasrecirculation valve 14 or via some other method measures. Thecorresponding emergency operation is selected and adjusted in dependenceupon the detected fault by the control apparatus 18 in correspondence tothe above cases. Thereafter, an input into a fault memory of the controlapparatus 18 takes place.

1. Method for operating an internal combustion engine (1), especially ofa motor vehicle, wherein fuel is injected into a combustion chamber (4)in a first operating mode during a compression phase and in a secondoperating mode during an induction phase, and wherein there is aswitchover between the operating modes, the engine (1) having anexhaust-gas recirculation with an exhaust-gas recirculation valve (14)characterized in that the engine (1) is switched into the firstoperating mode with an exhaust-gas recirculation valve (14) jammed inthe open state.
 2. Method of claim 1, characterized in that the engine(1) is switched into the second operating mode when the exhaust-gasrecirculation valve (14) is jammed in the closed state.
 3. Method of oneof the claims 1 or 2, characterized in that, for another fault functionof the exhaust-gas recirculation, the exhaust-gas recirculation valve(14) is closed and the engine (1) is switched into the second operatingmode.
 4. Method of one of the claims 1 to 3, characterized in that ajamming of the exhaust-gas recirculation valve (14) is determined withthe aid of a sensor.
 5. Control element, especially a read-only-memoryor flash memory, for a control apparatus (18) of an internal combustionengine (1), especially of a motor vehicle, on which a program is storedwhich is suitable for running on a computing apparatus, especially on amicroprocessor, and is suitable for carrying out a method of one of theclaims 1 to
 4. 6. Internal combustion engine (1), especially of a motorvehicle, including a combustion chamber (4) into which fuel can beinjected in a first operating mode during a compression phase and in asecond operating mode during an induction phase, the engine having acontrol apparatus (18) for switching over between the operating modesand an exhaust-gas recirculation having an exhaust-gas recirculationvalve (14), characterized in that the engine (1) can be switched intothe first operating mode by the control apparatus (18) when theexhaust-gas recirculation valve (14) jams in the open state.
 7. Controlapparatus (18) for an internal combustion engine (1), especially of amotor vehicle, the engine (1) having a combustion chamber (4) into whichfuel can be injected in a first operating mode during a compressionphase and in a second operating mode during an induction phase, thecontrol apparatus (18) being provided for switching over between theoperating modes, and the engine being provided with an exhaust-gasrecirculation having an exhaust-gas recirculation valve (14),characterized in that the engine (1) can be switched by the controlapparatus (18) into the first operating mode when the exhaust-gasrecirculation valve (14) is jammed in the open state.